Novel azo compounds, use in dyeing, compositions containing them and dyeing processes

ABSTRACT

Azo compounds of the 2-(4-amino)phenyldiazinecarboximidamide type and 2-(4-amino)phenylhydrazinecarboximidamide type, a process for their synthesis, their use for dyeing keratin fibers, dye compositions containing them, and dyeing processes.

[0001] The present invention relates to novel azo compounds of the2-(4-amino)phenyldiazinecarboximidamide type, to a process for theirsynthesis, to their use for dyeing keratin fibers, to dye compositionscontaining them and to dyeing processes using them.

[0002] It is well known that hair dye compositions use either oxidationdyes or direct dyes. The former dyes lead to shades with better coveringpower and better staying power, but they have the disadvantage of notbeing entirely harmless and of requiring an oxidation which is generallyaccompanied by appreciable degradation of the keratin fibers. Inaddition, their staying power and their affinity for the hair usuallyentails the appearance of the phenomenon of demarcation between dyedends and half-lengths and undyed roots.

[0003] These problems do not arise in the case of direct dyes. The useof direct dyes has the further advantage over oxidation dye precursorsof reducing the potential risks of allergy.

[0004] Among the direct dyes most commonly used are nitrobenzenederivatives. However, these nitrobenzene dyes do not sufficientlywithstand repeated washing. To overcome this flaw, attempts have beenmade to replace nitrobenzene dyes with aminoanthraquinone dyes or azodyes. It has already been proposed, in particular in patent applicationFR-A-2,570,946, to use the azo dye of the following formula:

[0005] i.e.4-amino-2′-methyl-4′-[N,N-bis(b-hydroxyethyl)amino]phenylazobenzene.

[0006] However, the use of this compound to dye the hair does not yieldentirely satisfactory results, in particular, regarding the intensity ofthe colourings obtained.

[0007] The inventors have thus sought other azo dyes which have goodsolubility in a medium suitable for dyeing, such as water, water/alcoholmixtures and more generally common dye supports and which give, onkeratin fibers, dyes with good resistance properties with respect to thevarious attacking factors to which keratin fibers may be subjected, andin particular with respect to washing, light, bad weather andperspiration.

[0008] Thus, following these investigations, the inventors havediscovered azo compounds of the 2-(4-amino)phenyldiazinecarboximidamidetype of formula (I) defined below.

[0009] This discovery forms the basis of the present invention.

[0010] The present invention is thus novel azo compounds of formula (I)below, and acid addition salts thereof:

[0011] in which:

[0012] R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical or a C₁-C₆ alkoxy radical; or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen;

[0013] R₃ and R₄, independently of each other, represent a hydrogenatom, a C₁-C₆ alkyl radical, a C₁-C₆ monohydroxyalkyl radical or a C₂-C₆polyhydroxyalkyl radical; and

[0014] A is a 5- to 6-membered aromatic ring which can be interrupted byone or more hetero atoms chosen from sulfur, nitrogen and oxygen, orfused to another 5- to 6-membered aromatic ring.

[0015] When used to dye keratin fibers, the compounds of formula (I) inaccordance with the invention have good solubility in water, inwater/alcohol mixtures and more generally in common dye supports, andgive colourings in a very intense coppery-orange shade which areparticularly resistant to the various treatments to which the fibers maybe subjected, such as washing, light, bad weather and perspiration. Thecoppery-orange colourings obtained using the compounds of formula (I) inaccordance with the invention are, in particular, more intense thanthose obtained under the same conditions with4-amino-2′-methyl4′-[N,N′-bis(b-hydroxyethyl)amino]phenylazobenzenementioned above.

[0016] In formula (I) above, the alkyl, monohydroxyalkyl andpolyhydroxyalkyl radicals may be linear or branched.

[0017] Among the C₁-C₆ alkyl radicals of the compounds of formula (I)above, preferred alkyl radicals are: methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl and isohexylradicals.

[0018] Among the C₁-C₆ monohydroxyalkyl radicals, preferred monohydroxylradicals are: hydroxymethyl, hydroxyethyl, hydroxypropyl andhydroxybutyl radicals.

[0019] Among the C₂-C₆ polyhydroxyalkyl radicals, preferredpolyhydroxylalkyl radicals are: dihydroxyethyl, dihydroxypropyl,trihydroxypropyl and dihydroxybutyl radicals.

[0020] Among the cycloalkyl radicals which can be represented by theradicals R₁ and R₂, preferred cycloalkyl radicals are: cyclohexyl andcyclopentyl.

[0021] Among the aromatic rings which can be represented by the radicalsR₁ and R₂, preferred aromatic rings are, for example, phenyl rings;phenyl rings substituted with a C₁-C₆ alkyl radical, a halogen atom oran amino, hydroxyl or C₁-C₆ alkoxy radical; benzyl, pyrimidine,pyridazine and benzimidazole rings.

[0022] Among the heterocycles which can be formed by the radicals R₁ andR₂ together, preferred heterocycles are: imidazole, benzotriazole,benzimidazole, pyrrolidine, piperidine and morpholine rings.

[0023] Among the rings which can be represented by the aromatic ring A,preferred rings are, for example, 6-membered rings such as phenyl,pyrimidine and pyridine rings, and 5-membered rings such as pyrrole andpyrazole rings.

[0024] The radicals R₁, R₂, R₃ and R₄, independently of each other,preferably represent a hydrogen atom or a methyl radical.

[0025] Among the compounds of formula (I), mention may be made inparticular of:

[0026] 2-(4-amino)phenyldiazinecarboximidamide,

[0027] N,N-dimethyl-2-(4-amino)phenyldiazinecarboximidamide,

[0028] N,N-diethyl-2-(4-amino)phenyldiazinecarboximidamide,

[0029] N,N-diisopropyl-2-(4-amino)phenyldiazinecarboximidamide,

[0030] N, N-dibutyl-2-(4-amino)phenyldiazinecarboximidamide,

[0031] 2-(5-amino)-2-pyridyldiazinecarboximidamide,

[0032] and the acid addition salts thereof.

[0033] The compounds of formula (I) in accordance with the invention canreadily be obtained, according to methods well known in the state of theart, which comprise, in a first step, carrying out, in a solvent medium,a reduction reaction on a compound of formula (III) below:

[0034] in which A, R₁ and R₂ can take the same meanings as thoseindicated above for the compounds of formula (I), to give a compound of2-(4-amino)phenylhydrazinecarboximidamide type of formula (II) below:

[0035] in which A, R₁, R₂, R₃ and R₄ have the same meanings as thoseindicated above for the compounds of formula (I), which product, in asecond step, is oxidized, in a solvent medium, to give the correspondingcompound of formula (I).

[0036] According to a variant of this synthetic process, and when, inthe compounds of formula (I), at least one of the radicals R₃ and R₄ isother than a hydrogen atom, the process then includes an intermediatestep of substituting the amine according to the known standard methods.

[0037] When the synthesis is complete, the compounds of formula (I) inaccordance with the invention can, where appropriate, be recovered bymethods which are well known in the state of the art, such ascrystallization or distillation.

[0038] The solvent(s) used in steps 1 and 2 above is (are) preferablychosen from water, C₁-C₄ alkanols such as methanol, ethanol orisopropanol, and mixtures thereof.

[0039] The reduction reaction used in the first step is preferably acatalytic hydrogenation, the catalyst being, for example, palladium oncharcoal.

[0040] The oxidizing agents which can be used in the second step arepreferably chosen from sodium iodate, sodium periodate, atmosphericoxygen, magnesium phthalate monoperoxide, hydrogen peroxide and hydrogenperoxide in the presence of metal salts such as, for example, manganesediacetate, potassium ferricyanide, silver oxide and ferric chloride.

[0041] The pH of the synthetic medium used in the first and second stepsis not a critical factor, and preferably ranges from approximately 4 to10. It can be adjusted using basifying or acidifying agents which arewell known in the state of the art.

[0042] The temperature of the reactions carried out in steps 1 and 2generally ranges from approximately 0 to 60° C.

[0043] Another aspect of the invention is the use of the compounds offormula (I) in accordance with the invention as dyes for dyeing keratinfibers, and in particular human keratin fibers such as the hair.

[0044] The intermediate compounds of formula (II) above can also be usedas dyes, and in particular as auto-oxidizing dyes (i.e. dyes which donot require the use of an oxidizing agent in order to give a colouring)for dyeing keratin fibers, in particular human keratin fibers such asthe hair.

[0045] Among the compounds of formula (II), preferred compounds are:

[0046] 2-(4-amino)phenylhydrazinecarboximidamide,

[0047] N,N-dimethyl-2-(4-amino)phenylhydrazinecarboximidamide,

[0048] N,N-diethyl-2-(4-amino)phenylhydrazinecarboximidamide,

[0049] N,N-diisopropyl-2-(4-amino)phenylhydrazinecarboximidamide,

[0050] N,N-dibutyl-2-(4-amino)phenylhydrazinecarboximidamide,

[0051] 2-(5-amino)-2-pyridylhydrazinecarboximidamide,

[0052] and the acid addition salts thereof.

[0053] Certain compounds of formula (II) above are novel per se and, inthis respect, constitute another aspect of the invention. These novelcompounds, and the acid addition salts thereof, correspond to formula(II′) below:

[0054] in which A, R₁, R₂, R₃ and R₄ have the same meanings as thoseindicated above for the compounds of formula (I), with the proviso thatat least one of the radicals R₁, R₂, R₃ and R₄ is other than a hydrogenatom.

[0055] 2-(4-Amino)phenylhydrazinecarboximidamide (compound of formula(II′) in which R₁, R₂, R₃ and R₄ simultaneously represent a hydrogenatom) is mentioned in an article by Petersen S. et al. (Angew. Chem.,67(1955), pages 217-231) with regard to quinone-based fungicides.

[0056] Among the compounds of formula (II′) in accordance with theinvention, preferred compounds are:

[0057] N,N-dimethyl-2-(4-amino)phenylhydrazinecarboximidamide,

[0058] N,N-diethyl-2-(4-amino)phenylhydrazinecarboximidamide,

[0059] N,N-diisopropyl-2-(4-amino)phenylhydrazinecarboximidamide,

[0060] N,N-dibutyl-2-(4-amino)phenylhydrazinecarboximidamide,

[0061] 2-(5-amino)2-pyridylhydrazinecarboximidamide,

[0062] and the acid addition salts thereof.

[0063] Yet another aspect of the invention is a composition for dyeingkeratin fibers, and in particular human keratin fibers such as the hair,that comprises, in a medium which is suitable for dyeing, at least onecompound of formula (I) in accordance with the invention and/or at leastone compound of formula (II) in accordance with the invention.

[0064] The compound(s) of formula (I) and/or the compound(s) of formula(II) preferably represent(s) from 0.0005 to 12% by weight approximatelyrelative to the total weight of the dye composition, and even morepreferably from 0.005 to 6% by weight approximately relative to thisweight.

[0065] The medium suitable for dyeing, such as water, water/alcoholmixtures and more generally common dye supports generally compriseswater or a mixture of water and at least one organic solvent to dissolveany compounds which are not sufficiently water-soluble. Preferredorganic solvents are, for example, C₁-C₄ lower alkanols, such as ethanoland isopropanol; glycerol; glycols and glycol ethers such as2-butoxyethanol, propylene glycol, propylene glycol monomethyl ether anddiethylene glycol monoethyl ether and monomethyl ether, as well asaromatic alcohols such as benzylalcohol or phenoxyethanol, similarproducts and mixtures thereof.

[0066] The solvents can be present in proportions preferably rangingfrom 1 to 40% by weight approximately relative to the total weight ofthe dye composition, and even more preferably from 5 to 30% by weightapproximately.

[0067] The pH of the dye composition in accordance with the inventiongenerally ranges from approximately 3 to 12, and preferablyapproximately from 5 to 11. It can be adjusted to the desired valueusing acidifying or basifying agents usually used to dye keratin fibers.

[0068] Preferred acidifying agents include, for example, inorganic ororganic acids such as hydrochloric acid, orthophosphoric acid, sulfuricacid, carboxylic acids such as acetic acid, tartaric acid, citric acidand lactic acid, and sulfonic acids.

[0069] Preferred basifying agents are, for example, aqueous ammonia,alkaline carbonates, alkanolamines such as mono-, di- andtriethanolamines and derivatives thereof, sodium hydroxide, potassiumhydroxide and the compounds of formula (IV) below:

[0070] in which W is a propylene residue optionally substituted with ahydroxyl radical or a C₁-C₆ alkyl radical; R₅, R₆, R₇ and R₈, which maybe identical or different, represent a hydrogen atom, a C₁-C₆ alkylradical or a C₁-C₆ hydroxyalkyl radical.

[0071] The dye composition in accordance with the invention can alsocontain various adjuvants conventionally used in hairdye compositions,such as anionic, cationic, nonionic, amphoteric or zwitterionicsurfactants or mixtures thereof, anionic, cationic, nonionic, amphotericor zwitterionic polymers or mixtures thereof, inorganic or organicthickeners, antioxidants, penetration agents, sequestering agents,fragrances, buffers, dispersing agents, conditioners such as, forexample, modified or unmodified, volatile or non-volatile silicones,film-forming agents, ceramides, preserving agents and opacifiers.

[0072] Needless to say, a person skilled in the art can select optionalcomplementary compounds such that the advantageous propertiesintrinsically associated with the dye composition in accordance with theinvention are not, or are not substantially, adversely affected by theaddition(s) envisaged.

[0073] The dye composition according to the invention can be in variousforms, such as in the form of liquids, creams or gels or in any otherform which is suitable for dyeing keratin fibers, and in particularhuman hair.

[0074] In particular, to facilitate the oxidation of the compounds offormula (II) in accordance with the invention, when oxidizing agents arepresent in the dye composition or when the composition contains at leastone oxidation dye precursor, the said composition can also contain oneor more oxidizing agents. These oxidizing agents can be chosen, inparticular, from hydrogen peroxide, urea peroxide, alkali metalbromates, persalts such as perborates and persulfates, and enzymes suchas peroxidases and two-electron oxidoreductases. It is particularlypreferred to use hydrogen peroxide or enzymes.

[0075] As has been mentioned above, the dye composition in accordancewith the invention can also contain one or more oxidation dyeprecursors, i.e. one or more oxidation bases and/or one or morecouplers. The oxidation bases can be chosen in particular frompara-phenylenediamines, para-aminophenols, orthophenylenediamines andheterocyclic bases such as, for example, pyridine derivatives,pyrimidine derivatives, pyrazole derivatives and pyrazolopyrimidinederivatives. The couplers can be chosen in particular frommeta-phenylenediamines, meta-aminophenols, meta-diphenols, heterocycliccouplers such as, for example, indole derivatives, indoline derivatives,benzimidazole derivatives, benzomorpholine derivatives, sesamolderivatives and pyridine, pyrimidine and pyrazole derivatives, and theacid addition salts thereof.

[0076] When present, the oxidation base(s) preferably represent(s) from0.0005 to 12% by weight approximately relative to the total weight ofthe dye composition in accordance with the invention, and even morepreferably from 0.005 to 8% by weight approximately relative to thisweight.

[0077] When they are present, the coupler(s) preferably represent(s)from 0.0001 to 10% by weight approximately relative to the total weightof the ready-to-use dye composition, and even more preferably from 0.005to 8% by weight approximately relative to this weight.

[0078] The dye composition according to the invention can also containone or more direct dyes which can be chosen in particular from azo dyesother than those of the invention, anthraquinones and nitro derivativesof the benzene series, in particular in order to modify the shades or toenrich them with glints.

[0079] In general, the acid addition salts which can be used in thecontext of the dye compositions of the invention (compounds of formulae(I), (II) and (II′), additional oxidation bases and couplers) are chosenin particular from the hydrochlorides, hydrobromides, sulfates,citrates, succinates, tartrates, lactates and acetates.

[0080] Another aspect of the invention is a process for dyeing keratinfibers, and in particular human keratin fibers such as the hair usingthe dye composition as defined above.

[0081] According to this process, at least one dye composition asdefined above is applied to the fibers for a period which is sufficientto develop the desired colouring, after which the fibers are rinsed,optionally washed with shampoo, rinsed again and dried.

[0082] The time required to develop the colouring on the keratin fiberspreferably ranges from 3 to 60 minutes and even more precisely from 5 to40 minutes.

[0083] According to one specific embodiment of the invention, and whenthe dye composition in accordance with the invention contains at leastone compound of formula (II) and at least one oxidizing agent, theprocess includes a preliminary step which comprises separately storing,on the one hand, a composition (A) comprising, in a medium which issuitable for dyeing, at least one compound, such as formula (II) asdefined above, and, on the other hand, a composition (B) containing, ina medium which is suitable for dyeing, at least one oxidizing agent, andthen in mixing them together at the time of use, before applying thismixture to the keratin fibers.

[0084] Another subject of the invention is a multi-compartment dyeingdevice or “kit” or any other multi-compartment packaging system, a firstcompartment of which contains composition (A) as defined above and asecond compartment of which contains composition (B) as defined above.These devices can be equipped with a means for delivering the desiredmixture onto the hair, such as the devices described in patentFR-2,586,913, the disclosure of which is specifically incorporated byreference herein.

[0085] The examples which follow are intended to illustrate theinvention without, however, limiting its scope.

PREPARATION EXAMPLES Preparation Example Synthesis of2-(4-amino)phenyldiazinecarboximidamide hydrochloride

[0086] 10 g of 2-(4-amino)phenylhydrazinecarboximidamide in 250 ml ofmethanol were placed in a 500 ml round-bottomed flask at roomtemperature. 20 g of silver oxide were then added and the mixture wasstirred for 30 minutes at room temperature. The reaction mixture wasthen filtered through a sinter funnel, 10 ml of 5.4 M hydrochloric acidin absolute ethanol were then added and the expected azo compound wasthen precipitated by adding 1000 ml of diisopropyl ether. By filtrationthrough a sinter funnel and washing with ethyl ether, 7.2 g of2-(4-amino)phenyldiazinecarboximidamide dihydrochloride, whichprecipitated in the form of a partially hydrated red solid, wereisolated; this compound melted with decomposition at 199° C. and theelemental analysis calculated was: % C H N Cl Calculated 35.61 4.7029.66 30.03 Found 34.11 4.93 27.46 30.72

Preparation Example 2 Synthesis ofN,N-dimethyl-2-(4-amino)phenyldiazinecarboximidamide hydrochloride

[0087] This compound was prepared and purified according to theprocedure described above for Example 1.

[0088] Starting with 7 g ofN,N-dimethyl-2-(4-amino)phenylhydrazinecarboximidamide and 14 g ofsilver oxide, 4.5 g of 2-(4-amino)phenyldiazinecarboximidamidehydrochloride were isolated in the form of a red solid; this compoundmelted with decomposition at 246.6° C. and the elemental analysiscalculated was: % C H N Cl Calculated 47.48 6.20 30.76 15.57 Found 46.176.32 30.04 14.08

Preparation Example 3 Synthesis ofN,N-dimethyl-2-(4-amino)phenylhydrazinecarboximidamide dihydrochloride

[0089] 4.0 g of N,N-dimethyl-2-(4-nitro)phenylhydrazinecarboximidamidein 100 ml of methanol were placed in a 250 ml reactor. 0.4 g ofpalladium on charcoal (containing 50% water and 10% active agent) wasthen introduced. The mixture was hydrogenated for 5 minutes at apressure of 2 bar, and then filtered through a sinter funnel. Thesolution was then acidified with 4 ml of hydrochloric ethanol and thenprecipitated by addition of 400 ml of diisopropyl ether. 3.5 g ofN,N-dimethyl-2-(4-amino)phenylhydrazinecarboximidamide dihydrochloridewere isolated in the form of a white solid; this compound melted withdecomposition at 185.5° C. and the elemental analysis calculated was: %C H N Cl Calculated 40.61 6.44 26.31 26.18 Found 39.76 6.61 25.20 26.64

Preparation Example 4 Synthesis of2-(4-amino)phenyl-hydrazinecarboximidamide dihydrochloride

[0090] 13.8 g of 2-(4-nitro)phenylhydrazinecarboximidamide in 400 ml ofa 95/5 methanol/N,N-dimethylformamide mixture were placed in a reactor.1.4 g of palladium on charcoal (containing 50% water and 10% activeagent) were then introduced. The mixture was hydrogenated for 5 minutesat a pressure of 2 bar and was then filtered through a sinter funnel.The solution was then acidified with 15 ml of hydrochloric ethanol andthen precipitated by addition of 1000 ml of diisopropyl ether. 6.5 g of2-(4-amino)phenylhydrazinecarboximidamide dihydrochloride were isolatedin the form of a white solid; this compound melted with decomposition at208° C. and the elemental analysis calculated was: % C H N Cl Calculated35.31 5.50 29.41 29.78 Found 35.03 5.71 27.85 30.40

Dyeing Examples Comparative Examples 1 and 2

[0091] The following dye compositions were prepared (contents in grams):EXAMPLE 1 (*) 2 4-Amino-2′-methyl-4′-[N,N-bis(b-hydroxy- 0.472 —ethyl)amino]phenylazobenzene (compound not forming part of theinvention) 2-(4-Amino)phenylhydrazinecarboximidamide — 0.099dihydrochloride (compound of formula (II)) Common dye support No. 1 (**)(**) Demineralized water q.s. 100 g 100 g

[0092] It is important to note that the composition of Example 2 has amolar concentration of dye which is significantly lower than that ofExample 1 (i.e. 3.75×10⁻⁴ mol as against 1.5×10⁻⁴ mol). Ethylene glycolmonoethyl ether 10 g Cetylstearyl alcohol/sodium lauryl sulfate mixturesold 2 g under the name Sinnowax SX^(å) by Henkel Oxyethylenated (3 EO)linear fatty alcohol (C₁₃-C₁₅) sold 3 g under the name Ukanil 25^(å) bythe company PCUK Oxyethylenated (7 EO) linear fatty alcohol (C₁₃-C₁₅)sold 2 g under the name Ukanil 43^(å) by the company PCUKTrimethylcetylammonium bromide 1.5 g Monoethanolamine q.s. pH 8

[0093] At the time of use, each of the above dye compositions wasapplied to locks of natural gray hair containing 90% white hairs, in aproportion of 15 g of composition per 3 g of hair, for 20 minutes. Thehair was then rinsed, washed with shampoo, rinsed again and then dried.

[0094] The hair dyed with compositions 1 and 2 had the sameorange-yellow shade.

[0095] In order to determine the increase in colouring more precisely,the color of the locks was evaluated, before and after dyeing, in theMunsell system, using a Minolta CM-2002® calorimeter.

[0096] According to the Munsell notation, a color is defined by theexpression HV/C in which the three parameters respectively denote theshade or Hue (H), the intensity or Value (V) and the purity orChromaticity (C), the oblique line in this expression simply being aconvention and not indicating a ratio.

[0097] The difference between the color of the lock before dyeing andthe color of the lock after dyeing expresses the intensity of thecolouring and was calculated by applying the Nickerson formula:

ΔE=0.4 C0ΔH+6ΔV+3ΔC

[0098] as described, for example, in “Couleur, Industries et Technique”;pages 14-17; Vol. No. 5; 1978.

[0099] In this formula, ΔE represents the color difference between twolocks, ΔH, ΔV and ΔC represent the variation in absolute values of theparameters H, V and C, and C₀ represents the purity of the lock withrespect to which it is desired to evaluate the color difference.

[0100] The greater the value of ΔE, the more intense the colouring.

[0101] The results are given in the table below: Color of Color of thehair the hair before after Intensity of the colouring COMPOSITION dyeingdyeing ΔH ΔV ΔC ΔE 1(*) 3.05 Y 1.85 Y 1.2 0.5 3.5 14.4 5.7/1.9 5.2/5.4 23.05 Y 1.58 Y 1.5 0.4 3.3 13.4 5.7/1.9 5.3/5.2

[0102] These results show that Composition 2 in accordance with theinvention gives a colouring which is essentially as intense as that ofcomposition 1, which does not form part of the invention and whichcontains a dye which does not form part of the invention, at a molarconcentration which is significantly larger than that used inComposition 2.

Examples 3 to 6 of Direct Dyeing

[0103] The following dye compositions were prepared (contents in grams):EXAMPLE 3 4 5 6 2-(4-Amino)phenylhydrazinecarb- 0.396 0.099 oximidamidedihydrochloride (compound of formula (II))N,N-Dimethyl-2-(4-amino)phenyl- — — 0.399 hydrazinecarboximidamidedihydrochloride (compound of formula (II))N,N-Dimethyl-2-(4-amino)phenyl- — — — 0.396 diazinecarboximidamidedihydrochloride (compound of formula (I)) Common dye support No. 1 (**)(**) (**) (**) Demineralized water q.s. 100 g 100 g 100 g 100 g

[0104] This is identical to the one used above for Examples 1 and 2.

[0105] Locks of natural gray hair containing 90% white hairs were dyedwith each of the above compositions according to the dyeing processdescribed above for Examples 1 and 2.

[0106] The shades obtained are given in the table below: EXAMPLE SHADEOBTAINED 3 Coppery orange 4 Yellow-orange 5 Yellow-orange 6 Red-orange

Examples 7 to 15 of Oxidation Dyeing

[0107] The following dye compositions were prepared (contents in grams):ATTORNEY DOCKET NO. 06028.0004-00 EXAMPLE 7 8 9 10 11 12 13 14 152-(4-Amino)phenylhydrazinecarboximidamide 0.74 0.74  0.74  0.74  0.740.74  0.74  0.74  dihydrochloride (compound of formula (II))N,N-Dimethyl-2-(4-amino)phenyl- — — — — — — — — 0.199hydrazinecarboximidamide dihydrochloride (compound of formula (II))para-Phenylenediamine (oxidation base) — — — — — 0.324 0.324 — —para-Aminophenol (oxidation base) — — — — — — — 0.327 —2,4-Diaminophenoxyethanol dihydrochloride — 0.723 — — — 0.723 — — —(coupler) 2-Methyl-5-N-(b-hydroxyethyl) aminophenol — — 0.504 — — — — —— (coupler) meta-Aminophenol (coupler) — — — 0.327 — — — 0.327 —Resorcinol (coupler) — — — — 0.33 — 0.33  — — Common dye support No. 2(***) (***) (***) (***) (***) (***) (***) (***) (***) Deminerlized waterq.s. 100 g 100 g 100 g 100 g 100 g 100 g 100 g 100 g 100 g

[0108] Oleyl alcohol polyglycerolated with 2 mol of 4.0 g glycerol Oleylalcohol polyglycerolated with 4 mol of 5.69 g A.M. glycerol, containing78% active material (A.M.) Oleic acid 3.0 g Oleylamine containing 2 molof ethylene oxide, 7.0 g sold under the trade name Ethomeen O12 ® by thecompany Akzo Diethylaminopropyl laurylaminosuccinamate, 3.0 g A.M.sodium salt, containing 55% A.M. Oleyl alcohol 5.0 g Oleic aciddiethanolamide 12.0 g Propylene glycol 3.5 g Ethyl alcohol 7.0 gDipropylene glycol 0.5 g Propylene glycol monomethyl ether 9.0 g Sodiummetabisulfite as an aqueous solution 0.455 g A.M. containing 35% A.M.Ammonium acetate 0.8 g Antioxidant, sequestering agent q.s. Fragrance,preserving agent q.s. Aqueous ammonia containing 20% NH₃ 10.0 g

[0109] At the time of use, each of the above dye compositions was mixed,weight for weight, with a 20-volumes hydrogen peroxide solution (6% byweight) of pH 3.

[0110] The mixture obtained was applied to locks of natural orpermanent-waved gray hair containing 90% white hairs, for 30 minutes.The locks were then rinsed, washed with a standard shampoo, rinsed againand then dried.

[0111] The shades obtained are given in the table below: EXAMPLE SHADEOBTAINED 7 Yellow-orange 8 Orange-brown 9 Orange 10 Red-orange 11Yellow-orange 12 Black-brown 13 Brown-orange 14 Yellow-orange 15Orange-yellow

What is claimed is:
 1. An azo compound of formula (I) or the acidaddition salt thereof:

in which: R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical, or a C₁-C₆ alkoxy radical; or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen; R₃ and R₄,independently of each other, represent a hydrogen atom, a C₁-C₆ alkylradical, a C₁-C₆ monohydroxyalkyl radical or a C₂-C₆ polyhydroxyalkylradical; and A is a 5- to 6-membered aromatic ring which can beinterrupted by one or more hetero atoms chosen from sulfur, nitrogen andoxygen, or fused to another 5- to 6-membered aromatic ring.
 2. Thecompound of claim 1 or salt thereof, wherein the C₁-C₆ alkyl radicalsare chosen from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,tert-butyl, n-pentyl, isopentyl, n-hexyl, and isohexyl radicals.
 3. Thecompound of claim 1 or salt thereof, wherein the C₁-C₆ monohydroxyalkylradical is chosen from hydroxymethyl, hydroxyethyl, hydroxypropyl, andhydroxybutyl radicals.
 4. The compound of claim 1 or salt thereof,wherein the C₂-C₆ polyhydroxyalkyl radical is chosen fromdihydroxyethyl, dihydroxypropyl, trihydroxypropyl, and dihydroxybutylradicals.
 5. The compound of claim 1 or salt thereof, wherein thecycloalkyl radical is chosen from cyclohexyl and cyclopentyl.
 6. Thecompound of claim 1 or salt thereof, wherein the aromatic rings arechosen from phenyl rings; phenyl rings substituted with a C₁-C₆ alkylradical, a halogen atom, an amino radical, a hydroxyl radical, or aC₁-C₆ alkoxy radical; benzyl, pyrimidine, pyridazine, and benzimidazolerings.
 7. The compound of claim 1 or salt thereof, wherein said 4- to8-membered heterocycle is chosen from imidazole, benzotriazole,benzimidazole, pyrrolidine, piperidine, and morpholine rings.
 8. Thecompound of claim 1 or salt thereof, wherein the aromatic ring A is a6-membered ring chosen from phenyl, pyrimidine and pyridine rings, or a5-membered ring chosen from pyrrole and pyrazole rings.
 9. The compoundof claim 1, wherein the compound or salt thereof is chosen from:2-(4-amino)phenyldiazinecarboximidamide,N,N-dimethyl-2-(4-amino)phenyldiazinecarboximidamide,N,N-diethyl-2-(4-amino)phenyldiazinecarboximidamide,N,N-diisopropyl-2-(4-amino)phenyldiazinecarboximidamide,N,N-dibutyl-2-(4-amino)phenyldiazinecarboximidamide,2-(5-amino)-2-pyridyldiazinecarboximidamide, and the acid addition saltsthereof.
 10. A method for dyeing keratin fibers comprising the step ofcontacting said fibers, for a time sufficient to achieve said dyeing,with a compound of formula (II) or the acid addition salt thereof:

in which: R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical, or a C₁-C₆ alkoxy radical; or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen; R₃ and R₄,independently of each other, represent a hydrogen atom, a C₁-C₆ alkylradical, a C₁-C₆ monohydroxyalkyl radical or a C₂-C₆ polyhydroxyalkylradical; and A is a 5- to 6-membered aromatic ring which can beinterrupted by one or more hetero atoms chosen from sulfur, nitrogen andoxygen, or fused to another 5- to 6-membered aromatic ring.
 11. A methodfor making a compound of formula (I) or the acid addition salt thereofcomprising the steps of: (a) carrying out a reduction reaction in asolvent medium on a compound of formula (III) below

 in which R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical, or a C₁-C₆ alkoxy radical; or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen; A is a 5- to6-membered aromatic ring which can be interrupted by one or more heteroatoms chosen from sulfur, nitrogen and oxygen, or fused to another 5- to6-membered aromatic ring; for a time sufficient to give a compound offormula (II) or the acid addition salt thereof:

 in which: R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical, or a C₁-C₆ alkoxy radical, or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen; R₃ and R₄,independently of each other, represent a hydrogen atom, a C₁-C₆ alkylradical, a C₁-C₆ monohydroxyalkyl radical or a C₂-C₆ polyhydroxyalkylradical; and A is a 5- to 6-membered aromatic ring which can beinterrupted by one or more hetero atoms chosen from sulfur, nitrogen andoxygen, or fused to another 5- to 6-membered aromatic ring; and (b)oxidizing the compound of formula (II) in a solvent for a timesufficient to give the compound of formula (I) or an acid addition saltthereof:

 in which: R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical, or a C₁-C₆ alkoxy radical; or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen; R₃ and R₄,independently of each other, represent a hydrogen atom, a C₁-C₆ alkylradical, a C₁-C₆ monohydroxyalkyl radical or a C₂-C₆ polyhydroxyalkylradical; and A is a 5- to 6-membered aromatic ring which can beinterrupted by one or more hetero atoms chosen from sulfur, nitrogen andoxygen, or fused to another 5- to 6-membered aromatic ring.
 12. A methodof dyeing keratin fibers comprising applying to said keratin fibers acompound of formula (I) or salt according to claim 1 for a timesufficient to obtain said dyeing.
 13. The method of claim 12, whereinsaid keratin fibers are human keratin fibers.
 14. The method of claim13, wherein said human keratin fibers are hair.
 15. The method of claim10, wherein the compound of formula (II) or salt thereof is chosen from:2-(4-amino)phenylhydrazinecarboximidamide,N,N-dimethyl-2-(4-amino)phenylhydrazinecarboximidamide,N,N-diethyl-2-(4-amino)phenylhydrazinecarboximidamide,N,N-diisopropyl-2-(4-amino)phenylhydrazinecarboximidamide,N,N-dibutyl-2-(4-amino)phenylhydrazinecarboximidamide,2-(5-amino)-2-pyridylhydrazinecarboximidamide, and the acid additionsalts thereof.
 16. The method of claim 10, wherein the compound offormula (II) or salt thereof is chosen from:N,N-dimethyl-2-(4-amino)phenylhydrazinecarboximidamide,N,N-diethyl-2-(4-amino)phenylhydrazinecarboximidamide,N,N-diisopropyl-2-(4-amino)phenylhydrazinecarboximidamide,N,N-dibutyl-2-(4-amino)phenylhydrazinecarboximidamide,2-(5-amino)-2-pyridylhydrazinecarboximidamide, and the acid additionsalts thereof.
 17. The compound of formula (II′) or an acid additionsalt thereof:

in which R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical, or a C₁-C₆ alkoxy radical; or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen; R₃ and R₄,independently of each other, represent a hydrogen atom, a C₁-C₆ alkylradical, a C₁-C₆ monohydroxyalkyl radical or a C₂-C₆ polyhydroxyalkylradical; and A is a 5- to 6-membered aromatic ring which can beinterrupted by one or more hetero atoms chosen from sulfur, nitrogen andoxygen, or fused to another 5- to 6-membered aromatic ring, with theproviso that at least one of the radicals R₁, R₂, R₃ and R₄ is otherthan a hydrogen atom.
 18. The compound or salt as claimed in claim 17,wherein said compound or salt is chosen from:N,N-dimethyl-2-(4-amino)phenylhydrazinecarboximidamide,N,N-diethyl-2-(4-amino)phenylhydrazinecarboximidamide,N,N-diisopropyl-2-(4-amino)phenylhydrazinecarboximidamide,N,N-dibutyl-2-(4-amino)phenylhydrazinecarboximidamide,2-(5-amino)-2-pyridylhydrazinecarboximidamide, and the acid additionsalts thereof.
 19. A composition for dyeing keratin fibers, wherein saidcomposition comprises, in a medium which is suitable for dyeing, atleast one compound chosen from compounds of formula (I) and saltsthereof:

in which: R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical, or a C₁-C₆ alkoxy radical; or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen; R₃ and R₄,independently of each other, represent a hydrogen atom, a C₁-C₆ alkylradical, a C₁-C₆ monohydroxyalkyl radical or a C₂-C₆ polyhydroxyalkylradical; and A is a 5- to 6-membered aromatic ring which can beinterrupted by one or more hetero atoms chosen from sulfur, nitrogen andoxygen, or fused to another 5- to 6-membered aromatic ring and compoundsof formula (II) and salts thereof:

 in which: R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical, or a C₁-C₆ alkoxy radical; or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen; R₃ and R₄,independently of each other, represent a hydrogen atom, a C₁-C₆ alkylradical, a C₁-C₆ monohydroxyalkyl radical or a C₂-C₆ polyhydroxyalkylradical; and A is a 5- to 6-membered aromatic ring which can beinterrupted by one or more hetero atoms chosen from sulfur, nitrogen andoxygen, or fused to another 5- to 6-membered aromatic ring.
 20. Thecomposition of claim 19 wherein said keratin fibers are human keratinfibers.
 21. The composition of claim 21 wherein said human keratinfibers are hair.
 22. The composition of claim 19, wherein said at leastone compound represents from 0.0005 to 12% by weight relative to thetotal weight of the dye composition.
 23. The composition of claim 22,wherein said at least one compound represents from 0.005 to 6% by weightrelative to the total weight of the dye composition.
 24. The compositionof claim 19, wherein said medium suitable for dyeing comprises water ora mixture of water and at least one organic solvent chosen from C₁-C₄lower alkanols, glycerol, glycols, glycol ethers and aromatic alcohols.25. The composition of claim 24 wherein said at least one organicsolvent is present in proportions ranging from 1 to 40% by weightapproximately relative to the total weight of the dye composition. 26.The composition of claim 25 wherein said at least one organic solvent ispresent in proportions ranging from 5 to 30%.
 27. The composition ofclaim 19, wherein said composition has a pH ranging from 3 to
 12. 28.The composition of claim 27, wherein said composition has a pH rangingfrom 5to
 11. 29. The composition of claim 19, wherein said compositioncontains an oxidizing agent.
 30. The composition of claim 29, whereinsaid oxidizing agent is chosen from hydrogen peroxide, urea peroxide,alkali metal bromates, persalts, and enzymes.
 31. The composition ofclaim 30, wherein said persalts are chosen from perborates andpersulfates.
 32. The composition of claim 19, wherein said compositioncontains at least one oxidation base and/or at least one coupler. 33.The composition of claim 32, wherein said at least one oxidation baserepresents from 0.0005 to 12% by weight relative to the total weight ofthe dye composition.
 34. The composition of claim 32, wherein said atleast one coupler represents from 0.0001 to 10% by weight relative tothe total weight of the dye composition.
 35. The composition of claim33, wherein said at least one oxidation base represents from 0.005 to 8%by weight relative to the total weight of the dye composition.
 36. Thecomposition of claim 34, wherein said at least one coupler representsfrom 0.005 to 8% by weight relative to the total weight of the dyecomposition.
 37. The composition of claim 19, further comprising atleast one adjuvant chosen from anionic, cationic, nonionic, amphotericand zwitterionic surfactants, anionic, cationic, nonionic, amphotericand zwitterionic polymers, inorganic and organic thickeners,antioxidants, penetration agents, sequestering agents, fragrances,buffers, dispersing agents, conditioners, film-forming agents,ceramides, preserving agents and opacifiers.
 38. The composition ofclaim 37 wherein said conditioners are chosen from modified andunmodified, volatile and non-volatile silicones.
 39. The composition ofclaim 19, wherein the said acid addition salts are chosen fromhydrochlorides, hydrobromides, sulfates, citrates, succinates,tartrates, lactates and acetates.
 40. The composition of claim 19,wherein the composition optionally contains one or more direct dyeschosen from anthraquinones, nitro derivatives of benzene, and azo dyesother than those chosen from formula (I) and (II).
 41. The compositionof claim 19, which is provided in the form of a liquid, a cream, a gelor any other form suitable for dyeing keratin fibers.
 42. A method fordyeing keratin fibers, comprising the step of applying at least one dyecomposition of claim 19 to the fibers for a period of time which issufficient to develop the desired colouring.
 43. The method of claim 42,wherein said keratin fibers are human keratin fibers.
 44. The method ofclaim 43, wherein said human keratin fibers are hair.
 45. The method ofclaim 42, wherein said period of time ranges from 3 to 60 minutes. 46.The method of claim 45, wherein said period of time ranges from 5 to 40minutes.
 47. The method of claim 42, further comprising, prior to saidapplying step, the preliminary step of separately storing: a composition(A) comprising, in a medium which is suitable for dyeing, at least onecompound of formula (II) and a composition (B) containing, in a mediumwhich is suitable for dyeing, at least one oxidizing agent, and the stepof then mixing said separately stored components together at the time ofuse and prior to said applying step.
 48. A multi-compartment dyeingdevice or kit for dyeing keratin fibers, comprising at least twocompartments, wherein a first compartment contains composition (A)comprising, in a medium which is suitable for dyeing, at least onecompound of formula (II) or the acid addition salt thereof:

 in which: R₁ and R₂, independently of each other, represent a hydrogenatom; a C₁-C₆ alkyl radical; a 5- or 6-membered cycloalkyl radical; a 5-or 6-membered aromatic ring; a 5- or 6-membered aromatic ringsubstituted with a C₁-C₆ alkyl radical, a halogen atom, an aminoradical, a hydroxyl radical, or a C₁-C₆ alkoxy radical; or R₁ and R₂form, together with the nitrogen atom to which they are attached, a 4-to 8-membered heterocycle, said heterocycle containing one or morehetero atoms chosen from sulfur, nitrogen and oxygen; R₃ and R₄,independently of each other, represent a hydrogen atom, a C₁-C₆ alkylradical, a C₁-C₆ monohydroxyalkyl radical or a C₂-C₆ polyhydroxyalkylradical; and A is a 5- to 6-membered aromatic ring which can beinterrupted by one or more hetero atoms chosen from sulfur, nitrogen andoxygen, or fused to another 5- to 6-membered aromatic ring, and a secondcompartment contains composition (B) containing, in a medium which issuitable for dyeing, at least one oxidizing agent.